The present invention relates to an improved coil rack for a transformer, and more particularly to a transformer coil rack that is provided with means for guiding free ends of an inner coil winding of the transformer, so that the free ends of the inner coil winding can be axially pulled downward and then radially pulled outward to reach and be welded to terminals at outer ends of the coil rack. The guiding means prevent the free ends of the inner coil winding from contacting with an outer coil winding wounded around the inner coil winding and therefore prevent any possible short circuit caused by such contact.
A transformer mainly includes a coil rack around which an inner coil winding, a first insulating layer, an outer coil winding, and a second insulating layer are sequentially provided. Free ends of the inner and the outer coil windings are extended outward to be welded to terminals provided on the coil rack. The insulating layers prevent short circuit caused by undesirable contact of the inner coil winding with the outer coil winding.
FIG. 1 illustrates a conventional coil rack 10 that provides a coil winding seat 11. Radially extended channels 12 are provided on a lower surface of the coil winding seat 11 to end at two outer ends of the coil rack 10. There are also terminals 13 connected to the outer ends of the coil rack 10 for connecting free ends of inner and outer coil windings 14, 15 thereto. The terminals 13 are also used to connect the coil rack 10 to an electronic substrate (not shown).
As shown in FIG. 2, the inner coil winding 14 is provided around the coil winding seat 11 first. A first insulating layer 16 is then provided around the inner coil winding 14. Free ends of the inner coil winding 14 are pulled outward to pass through two of the channels 12 and finally welded to the terminals 13 adjacent to the channels 12. Then, the outer coil winding 15 is provided around the first insulating layer 16 and free ends of the outer coil winding 15 are welded to the other terminals 13. Finally, a second insulating layer 16 is provided around the outer coil winding 15 to form a transformer as shown in FIG. 3.
After the inner and the outer coil windings 14, 15 are sequentially provided around the coil winding seat 11, their free ends must be pulled outward along the channels 12 for them to be welded to the terminals 13. Since the channels 12 are radially extended through the lower surface of the coil winding seat 11, the free ends of the inner coil winding 14 being radially pulled outward along the channels 12 tend to contact with the outer coil winding 15 easily, as illustrated in FIG. 2, that will cause not only dangerous short circuit but also high bad yield in the production of transformers.